In 2006 David Tennant took part in the BBC One show Who Do You Think You Are? At the start of his journey, he knew very little about his background, other than the fact that he and his family had been brought up in Glasgow, and that there was some Irish blood in his veins. This information came from his maternal grandmother, Nellie Blair, who had been born in Londonderry. She had met her husband, Archie McLeod, while he was playing for the local football team, Derry City. He had been lured to Northern Ireland by the prospect of being paid good money to play the game that he loved. Indeed, he was quite a success, having previously been awarded a cap for Scotland as a junior and eventually becoming Derry City's top scorer. He met and married Nellie, a beautiful local girl in the 'Posh and Becks'-style big romance of the day.

Archie's roots were very different, and after an injury halted his playing career, he returned to his native Glasgow to work in a shipyard. Yet his family had not always been based in Scotland's industrial heartland. Archie's grandfather, Donald, had been born and raised in Mull, a rural setting where for centuries farming had been the main profession. Donald was born there in 1819, one of ten children, and his parents, Charles and Catherine, lived in a small stone cottage on the estate of the local landlord on the settlement of Inivey. Out of necessity they were largely self-sufficient, relying on potatoes, oats and barley to survive - the barley being used to make whisky! Yet in 1832, their lives were to radically change. The economic conditions of the day meant that landlords sought to maximise profits from their land by switching to sheep farming. To facilitate this, rents were raised and tenants who could not pay were forcibly evicted. As a consequence, by the end of the 19th century the Scottish Highlands were one of the most sparsely populated parts of western Europe. Families such as the McLeods were forced to journey south to places such as Glasgow to earn a living. Their stone cottages still litter the empty countryside to this day.

Nellie Blair's background is equally revealing about the history and social tensions that have affected Londonderry throughout the 20th century. Nellie was brought up a staunch Protestant, and her father William was a member of the Hamilton Marching Band, which led the annual Orange Order marches in commemoration of William of Orange's relief of Londonderry in the 17th century. In 1912, when Irish Nationalists looked like achieving their goal of Home Rule, half-a-million Protestants signed the Ulster Covenant protesting against the plans. William and his wife Agnes were among the signatories. When World War One broke out in 1914, he joined up with the Royal Army Medical Corps and saw his friends and comrades mown down at the Battle of the Somme in 1916. On returning home, he walked straight into another conflict between the British Army and the Irish Republican Army. The resulting treaty that divided Ireland into the province of Northern Ireland and the Irish Free State left William and his family only four miles within the British side of the border. His father, James, was a local councillor in Londonderry and was involved in the vote-rigging which maintained control of the council for the Protestant minority. Yet James also fought for social justice, and one of his daughters married a Catholic lad. His descendants were caught up in the Bloody Sunday march in 1972, the catalyst for the Troubles that have gripped the province ever since.